Conventional hydraulic operation controlling units, which are provided with a hydraulic pump that is operated by an engine and a hydraulic actuator that is operated by pressurized oil that is discharged from this hydraulic pump, and are formed in such a manner that the output properties of the engine are set in accordance with the work mode and the properties of the hydraulic pump are controlled so as to correspond to thus set output properties of the engine, as well as hydraulic excavators provided with the same have been known (see, for example, Patent Document 1). Here, in the hydraulic operation controlling unit that is proposed in this Patent Document 1, fluctuation in the engine speed due to the pump load is detected by an actual engine speed signal from an engine speed sensor and a throttle signal from a potentiometer that is attached to the fuel dial, the controller receives these signals and carries out an arithmetic operation, the result is sent to a TVC (Torque Variable Control) valve as a signal, and this TVC valve controls the amount of oil discharged by the hydraulic pump, and thereby, the output torque of the engine and the absorption torque of the hydraulic pump are always optimally matched with each other. In addition, when the pump load becomes excessive and the engine speed is reduced, the amount of oil discharged by the hydraulic pump is reduced as a result of a so called engine revolution sensing control, and thereby, the actual engine speed is instantly returned to the engine speed that corresponds to the rated output point so that the hydraulic pump can stably absorb the maximum horsepower of the engine so as to work highly efficiently.
Patent Document 1: Japanese Unexamined Patent Publication H2 (1990)-38630
In this type of the conventional hydraulic operation controlling unit, the present engine speed (the maximum engine speed without any load) is set at N7 as shown in FIG. 8, for example, in active mode where the engine is set so as to correspond to the work that requires both speed and power, and thereby, an engine output torque property line EL1 having a regulation line R1 is set. In this active mode, the hydraulic pump absorbing torque property line PL1 is set so that the hydraulic pump absorbs the output torque value T4 at the output torque point M4 (hereinafter, referred to as “matching point M4”) where the output of the engine becomes maximum, and thereby, the output torque of the engine and the absorbing torque of the hydraulic pump coincide with each other at matching point M4. Meanwhile, in the economy mode, which is set so as to correspond to usual excavating work while achieving reduction in the fuel cost, as shown in the figure, the engine speed (the maximum engine speed without any load) is set at the engine speed N5 which is smaller than engine speed N7 in the active mode by a predetermined number of revolutions, and thereby, the engine output torque property line EL50, having a regulation line R50 that is set on the lower speed side of the above described regular line R1, is set. In this economy mode, in order for the hydraulic pump to absorb the output torque value T3 that corresponds to the output torque point M3 (hereinafter, referred to as “matching point M3”) where the fuel efficiency of the engine is relatively high, in other words, the fuel consumption ratio (g/kw·h) of the engine is relatively low so as to make the engine operate efficiently, the absorbing torque of this hydraulic pump is controlled along equi-horsepower property line PL50 and the output torque of the engine and the absorbing torque of the hydraulic pump can be made to coincide with each other at the matching point M3.